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Greetings all, first post here

My nephews 1989 civic has a wierd problem where if driven at a consistent RPM for say two or three miles, it starts to misfire badly. To get it to stop, you have to slow down, shifting iinto the lower gears, and it after a few minutes shifting around and chaning the RPM.s it will recover.

The odd thing is that you can drive it around town all day and the problem does nto occur. By that I mean, if you are shifting around as you would in around town traffic, no problem. But get out on highway (or a local road) and ride alond in topo gear for a few miles and the problem starts.

Some particulars:

1989 civic hatchback, five speed (of course).
dual ppoint programed fuel injection
228,000 miles
AC, but not hooked up
New air filter on a cold air tube (the old one was clogged, but a new one didnt fix the issue. Also ran it with raw air (no filter) but no change in behaivior)
Replaced all the vacum lines that I could find, accept the ones on the automatic choke (didnt change the behavior)
Happens with the engine hot or cold
Idles fine
Revs through RPMS smooth as silk when shifting

Thoughts?

 
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Moved to your generation subforum. Hopefully you will have more luck getting help here.

 
Rep Power: 235

Sounds like a clogged fuel filter. If not that it could be your fuel pump is dying, bad fuel pressure regulator, or bad injectors.